Pacing apparatus and method utilizing improved catheter

ABSTRACT

Improved apparatus and method for temporary pacing, comprising a catheter having a first electrode positioned for placement in the patient&#39;&#39;s heart and a second electrode positioned to be within the patient&#39;&#39;s body but sufficiently proximal that it is outside the patient&#39;&#39;s heart, the second electrode having a surface area about an order of magnitude greater than the first, the electrodes being connected through respective leads within the catheter to a pacemaker (registered trademark, U.S. Patent Office), with the first electrode connected as the cathode.

United States Patent 1 Preston [451 July 8,1975

[ PACING APPARATUS AND METHOD UTILIZING IMPROVED CATHETER [76] Inventor:Thomas A. Preston, 820 37th Ave,

Seattle, Wash. 98122 [22] Filed: Nov. 28, 1972 [21] App]. No.: 309,996

[52] US. Cl. 128/419 P; 128/404 [51] Int. Cl A6ln 1/36 [58] Field ofSearch 128/404, 418, 419 P, 421, 128/422 [56] References Cited UNITEDSTATES PATENTS 3,416,533 12/1968 Fisher et a1 128/419 P 3,478,74611/1969 Greatbatchflmn. 128/419 P 3,788,329 1/1974 Friedman 128/419 P3,815,611 6/1974 Denniston 128/419 P OTHER PUBLlCATlONS Rogel et al.,Journal of Thoracic & Cardiovascular Surgery," Vol. 61, No. 3, March,1971, pp. 466-471. USCl Catalog, No. 5070021 9/72.

Schwedel et al., Annals-New York Academy of Sciences," Vol. 111, Art. 3,pp. 972-980, June 1 l, 1964.

Primary Examiner-William E. Kamm Attorney, Agent, or Firm-Bowie,Benasutti and Preston 5 7 1 ABSTRACT lmproved apparatus and method fortemporary pacing, comprising a catheter having a first electrodepositioned for placement in the patient's heart and a second electrodepositioned to be within the patient's body but sufficiently proximalthat it is outside the patients heart, the second electrode having asurface area about an order of magnitude greater than the first, theelectrodes being connected through respective leads within the catheterto a pacemaker (registered trademark, US. Patent Ofiice), with the firstelectrode connected as the cathode.

23 Claims, 4 Drawing Figures ABOUT 6 cm.

ABQUT 23 cm *A'TFt-WFHJUL 8 ms 3,893,461

EXTERNAL JUGULAR VEINS LEFT SUBCLAVIAN VEIN RIGHT SUBCLAVIAN VEINUPERIOR VENA INTERIOR VENA CAVA Fig. I

ABOUT 6cm.

ABOUT 23 cm.

:0 DISTAL ELECTRODE Fig 2b Fig. 2a

1 PACING APPARATUS AND METHOD UTILIZING IMPROVED CATHETER BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention lies in the areaof heart pacing apparatus and, more particularly, in the area ofcatheters used with external and implanted Pacemaker for temporary andpermanent pacing in a clinical environment. The apparatus and method ofthis invention are particularly adapted for demand pacing.

2. Description of the Prior Art Temporary pacing of a patient in thepost-operative period following cardiac surgery is an established andeffective means of treating arrhythmias or increasing cardiac output.Additionally, temporary pacing is particularly important and widely usedwith respect to complete heart block, especially in patients undergoingacute myocardial infarction. Such temporary pacing has been a widelyused clinical procedure in this country for many years, and thetechnique of inserting the catheter into the patient and pacing from anexternal source is a common technique of cardiology. A number ofinstrument manufacturers produce clinically acceptable catheters, andthere are several models of Pacemakers well known to cardiologists andsuitable for carrying out this technique,

There have been two basic types of catheters available and in use forsuch external, or temporary pacing. A first type is what is referred toas a unipolar catheter, having one lead extending substantially thelength of the catheter and being electrically connected to an electrodewhich is positioned inside the patients heart for transmitting thedesired electrical signal thereto. This cardiac electrode is connectedthrough the catheter lead to a first terminal of a Pacemaker devicewhich, in temporary pacing, is external to the patient, and which isdesigned to produce a desired periodic pacing signal. The secondterminal of the external Pacemaker is connected to an electrode which isgenerally clamped to the patients skin around or near the point of entryof the catheter, which may be approximately at the large vein oppositethe patients right elbow. Another suitable site, such as in the femoralvein, may also be used for catheter insertion. Such electrode must bemaintained in firm electrical contact with the patient, usuallyrequiring some sort of electrically conductive paste be applied to thepatients skin, as well as the use of additional means (such as suturingan electrode beneath the skin at the site of incision) for maintainingthe electrode in firm position. The time required to attach the secondelectrode to the patients skin is considered, by most physicians, to beat best a considerable annoyance, and external electrodes attached tothe skin are unreliable and require constant attention. When both theexternal electrode and the electrode which is placed in the patientsheart are connected to the Pacemaker, the periodic output signals fromthe Pacemaker terminals produce biopotentials in the patients heart of acharacter so as to induce stimulation of the heart, i.e., so as to pacethe heart.

The second type of standard catheter in common use, and clearly thepreferred type, is what is referred to as a bipolar catheter. havingboth electrodes positioned near the distal end of the catheter, suchthat when the catheter is fully inserted into the patients heart, bothelectrodes are inside the heart and in proper position to transmit thedesired signal from the Pacemaker directly to the patients heart. Theadvantage of the bipolar catheter over the unipolar form is the obviousone of eliminating the requirement of making an external attachment ofone electrode to the patients skin. Using the bipolar catheter, the twoleads of the catheter are simply connected directly to the externalPacemaker, or to whatever device is in clinical use.

There are two basic reasons which lead to the conclusion that the newand novel catheter design of this invention is not only advantageous butshould 'be required for safe clinical use. The first of these concernsthe phenomenon of induced ventricular arrhythmias associated with theuse of artifical Pacemaker. The possibility of Pacemaker inducedventricular arrhythmias has been recognized for some time, but theextent of the clinical risk of such arrhythmias has not been known. Infact, research has shown that an electronic Pacemaker stimulus can causea dangerous arrhythmia by falling during the vulnerable period of apreceding ventricular beat. This possibility exists most commonly whenan asynchronous artifical Pacemaker is in competition with normal sinusrhythm or ectopic beats from any source. The problem is particularlyimportant in patients requiring pacing during acute myocardialinfarction, as these patients are most susceptible to lifethreateningventricular arrhythmias.

l have found evidence that ventricular arrhythmias are evoked by anodalstimulation, which evidence suggests that in the majority of instancesan anode on or within the heart, of size and configuration to permitanodal stimulation, is necessary to produce ventricular tachycardia orventricular fibrillation in humans with permanent or temporary pacingsystems. All the available evidence points to the anode as the mostcommon site or origin of Pacemaker induced ventricular fibrillation.Although commercially available Pacemakers have outputs which areprobably too small to produce arrhythmias in normal human hearts, suchunits must be designed to produce stimuli exceeding the excitationthresholds of percent or more of all patients encountered. With time theexcitation threshold for an implanted electrode system can rise to 10times the initial implantation threshold, and therefore Pacemakers aredesigned to deliver 10-30 times as great a stimulus as is required foreffective pacing at the time of electrode implantation. Thus, underadverse conditions, such as acute myocardial infarction, etc., Pacemakerinduced ventricular arrhythmias are possible, especially if the anode ispositioned on or inside the ventricle.

As a result of the above conclusions, it is clear that only unipolarcathodal pacing should be used. As most pacing in a clinical situationis through temporary catheter electrodes, either a remote indifferentelectrode (anode), or catheter with a distal pacing cathode and a largeproximal anode, i.e., an anode at least ten times the surface area ofthe cathode, and positioned outside of the right ventricle, should beused. Since, as was discussed hereinabove, there is an overwhelmingpreference for a bipolar type of cathode which eliminates therequirement of attaching an electrode externally to the patients skin,there is a need for a catheter construction having a first (cardiac)electrode which is adapted to be positioned within the heart, and asecond electrode positioned such that it will be within the patientsbody, but outside of and proximal to the heart and preferably of greatersurface size than the cardiac elec trode. Furthermore, the cardiacelectrode should be used as the cathode, and the proximal electrode asthe anode.

The second discovery which has led to my novel catheter apparatusdesign, and method for use of same, relates to the use of demand, ornon-competitive Pacemakers. In the demand Pacemaker, the pacing signalis generated only upon demand, i.e., when the natural pacing signal ofthe patient is not sensed. For ventricular pacing, such demandPacemakers are commonly used to avoid competition with sinus or ectopicbeats. Competition between artificial and natural Pacemakers can resultin an unacceptable increase in heart rate and may precipitate seriousventricular arrhythmias. I have recently encountered samples of failureof proper demand function in the post-operative period resulting ineither of these complications, and at each case the failure was due to alow voltage signal coming from the bipolar electrodes of the catheter inuse, and normal demand function was restored by conversion to a unipolarsystem.

Although epicardial voltages in a bipolar system are usually well inexcess of those required for demand function, in any heart bipolarelectrodes can be positioned so as to detect a signal too small fordemand sensing. A bipolar system adequate to detect sinus beats may notdetect beats from a different origin such as ectopic ventricular beats.However, in every case that l have observed, regardless of the amplitudeof the bipolar electrogram, a unipolar electrogram could be obtainedwhich was greater in magnitude and sufficient for proper demandfunction. Conversion of a bipolar electrode system to a unipolar system,with only one electrode in the heart, results in a simple and effectivemeans of increasing the signal detected by the Pacemaker.

SUMMARY OF THE INVENTION It is the primary object of this invention toprovide catheter apparatus and a method for artificial pacing of apatient's heart, which has the advantages of a bipolar electrode systemin terms of ease of clinical use but which avoids the disadvantages of abipolar electrode, and particularly which provides that the anode beoutside of the patients heart, and which provides efficient pickup fordemand pacing.

In accordance with the above object, there is provided catheterapparatus for pacing of a patients heart comprising a catheter having afirst electrode, utilized as a cathode, positioned on the catheter suchthat it is within the patients heart when the catheter is fullypositioned, and having a second electrode, utilized as an anode, andpositioned proximal to the first electrode, having a surface area muchlarger than that of the cardiac electrode, and positioned so that it isexternal to the patient's heart during the pacing operation. Pacing isachieved by periodically delivering the pacing signal between a cathodepositioned within the heart and an anode positioned outside of theheart.

It is another object of this invention to provide an improved apparatusand method for temporary pacing of a patient by which pacing signals aregenerated outside of the heart, transmitted within the patient through acatheter of improved design, and connected between a first electrodepositioned within the patients heart and a second electrode positionedwithin the patient and outside of the patient's heart.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic sketchshowing the placement of a catheter within a human body, and whichindicates the critical areas of electrode placement according to thisinvention.

FIG. 2 is a sketch showing the catheter apparatus of this invention incombination with an artificial Pacemaker.

FIG. 2a is a detail sketch showing the connection of the anode of thecatheter of this invention to one of the catheter electrical leads.

FIG. 2b is a detail sketch showing the connection of the cathode of thecatheter of this invention to the other of the catheter leads.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, thereis shown a diagrammatic sketch of a catheter 20 inserted into a human.Most commonly, the catheter is inserted at about position 21, into theright basilic vein. The tip of the catheter is manipulated through thesuperior vena cava, the right atrium, and into the right ventricle. Thecatheter may also be introduced through the external (or internal)jugular veins, subclavian veins, or femoral veins. At the end portion ofa bipolar catheter external to the body a pair of electrical leads (orone lead for a unipolar) are connected to the Pacemaker for pacing.There are a number of commercially available Pacemakers which may beused in the practice of this invention. Such Pacemakers, and theirmanner of use, are well known to cardiologists.

In a commonly used prior art bipolar catheter, the two electrodes areboth caused to reside in the right ventricle, as shown at 24, 25. When aprior art unipolar catheter is utilized, there is only one heartelectrode, such as 24, and a second electrode is placed upon thepatient's skin near the point of entry at 21. The same catheterapparatus is utilized for demand pacing.

Referring now to FIG. 2, there is shown a diagrammatic sketch of thecatheter utilized in the practice of this invention, connected to aPacemaker 32. Pacemaker 32 may be either a conventional Pacemaker typedevice or a demand type Pacemaker device. The catheter is an elongatedand flexible instrument, constructed preferably of a plastic materialsuch as nylon or Teflon, and of generally tubular form withsubstantially constant outer diameter fron end to end. The catheter ofthis invention has two electrical leads 34, 35, constructed ofelectrically conductive material, and embedded in the non-conductiveplastic material. The larger of the two electrodes, 38, suitably acylindrical ring, of conductive material, is positioned so that when thecatheter is in place within the patient, it is outside of the patientsheart. It is connected to a first of the catheter leads, 34, as shown inFIG. 2a, which in turn is connected to the positive terminal ofPacemaker 32, such that it is the anodal electrode. At the far distalend of the catheter, near the tip thereof, is an electrode 40, whichalso is suitably a ring of conductive material around the outside of thecatheter, and in electrical contact with the other of the two conductingleads, 35, as shown in FIG. 2b. Lead 35 in turn is connected to thenegative terminal of Pacemaker 32, such that electrode is the cathodalelectrode. This electrode is of relatively small surface area, andtypically has a width of about 1-3 millimeters. For a catheter withoutside circumference of approximately 6-10 millimeters, the totalsurface area would be approximately 6-24 square millimeters.

In accordance with the discussion hereinabove, and in order to achievethe purpose of avoiding anodal stimulation of the heart, it has beenfound that the second electrode, which is used as the anode, should beplaced preferably at least 4 centimeters proximal to the heart (to theright atrium). This point is indicated in FIG. 1 by the dashed lineindicated at 50. In addition, to accommodate the occurrences where thecatheter may be introduced through the subclavian vein, the anode shouldnot extend beyond the region indicated approximately by the dashed line52. For a typical human, the distance from the distal electrode(cathode) to dashed line 50 is about 23 centimeters, and the distancefrom dashed line 50 to dashed line 52 is about an additional 6centimeters. Accordingly, the proximal electrode (anode) is suitablyplaced within this 6 centimeter distance (but need not be that long).For a catheter having an outside diameter of 2-3 millimeters, thesurface of the anode should be about 100-300 square millimeters.

It is highly desirable that the proximalanode be much larger in surfacearea than the cathode, in order to distribute the anodal-induced, orpositive-induced electric field intensity, so as not to stimulatesurrounding structures. By making the anode at least about 10 times aslarge as the cathode in surface area, this is achieved.

In practice, the distal electrode of the catheter is made the cathode byconnecting it to the negative terminal of the Pacemaker 32, and theproximal electrode is made the anode by connecting it, through lead 35,to the positive terminal of Pacemaker 32. It is seen that, in clinicaluse, the apparatus of this invention provides that the anode ispositioned safely outside of the patient's heart, and preferably atleast 4 centimeters away from the patients heart, while the cathode ispositioned within the patients right ventricle. By thus placing theanode outside of the heart, and in addition providing the anode with asurface area much larger than that of the cathode (so as to reduceelectric field concentration around the anode) the possibility ofanodalstimulation of the heart is effectively eliminated, and cathodal pacingis ensured. At the same time, however, the apparatus of this inventionprovides the advantages of the bipolar catheter, in that both electrodesare permanently affixed to the catheter, and there is no need forexternal placement of an electrode upon the patients skin. At the sametime, the positioning of the electrodes in accordance with thisinvention provides an effective unipolar type of pickup from the heart,so that when the catheter apparatus of this invention is used with ademand Pacemaker, the danger of detection of less than threshold signalsis substantially reduced.

It is to be understood that in order to ensure against anodalstimulation, it is desirable both to remove the anode from the vicinityof the heart and to make the surface area of the anode large. Althoughthe design as shown in FIG. 2 is considered to be the best and safestdesign, it is to be understood that improvement over prior art forms ofcatheters may be achieved with various compromise designs. For example,if the anode were to extend into the heart, but had a large and extendedsurface area such as would be obtained if the anode were continuousalmost to the point of entry, the

distribution of the large anode surface would mitigate against anodestimulation. Similarly, simply positioning the anode outside of theheart, but making it of the same order of magnitude and surface size asthe cathode, would achieve some improvement over the prior art. Whilethe design criterion of positioning the anode at least 4 centimetersexternal to the heart is a critical limitation necessary to ensure afactor of safety against anodal stimulation, placement of the anodewithin less than 4 cennmeters of the heart would still be an improvementover the prior art in accordance with the principles of this invention.Similarly, the design criterion of making the anode at least 10 times asgreat as the cathode is also a critical limitation necessary to ensureagainst anodal stimulation, but use of an anode of lesser size wouldstill be within the broad scope of this invention.

1 claim:

1. Catheter apparatus adapted to be positioned in a patient for use incardiac pacing of the patient, with a predetermined end extending intothe patients heart, comprising:

a. an elongated flexible catheter tube having two conducting leadsextending through respective lengths thereof;

b. a distal electrode of predetermined surface size positioned near saidpredetermined end of said catheter tube, and connected electrically to afirst of said leads; and

c. proximal electrode positioned on said catheter at a distance at leastabout 23 cm from said distal electrode, and connected electrically tothe second of said leads.

2. The apparatus as described in claim I, wherein said proximalelectrode has a surface area at least 10 times as great as said distalelectrode.

3. The apparatus as described in claim 2, wherein said proximalelectrode is positioned a distance within a range of 23-29 cm proximalfrom said distal electrode.

4. The apparatus as described in claim 1, wherein said proximalelectrode extends less than 6 centimeters along said catheter tube.

5. The apparatus as described in claim 1, wherein said proximalelectrode is of greater surface area than said distal electrode.

6. Pacing apparatus adapted for generating electrical pacing signalsoutside of a patient, communicating said signals inside of the patient,said delivering said signals between a position within the heart of thepatient and a position external to said heart, comprising:

a. a catheter adapted for insertion into a patient, having a distalelectrode positioned near a first end thereof, a proximal electrode onsaid catheter and positioned a distance at least 23 cm from said distalelectrode, a first lead connecting said distal electrode with theopposite end of said catheter, and a second lead connecting the proximalelectrode with said opposite catheter end,

b. signal generating means, for generating electrical pacing signals,said signal generating means having first and second terminals acrosswhich said electrical signals appear;

c. connecting means for connecting, at said opposite end of saidcatheter, said first lead to the first terminal of said signalgenerating means and said secsaid proximal electrode is positioned at adistance within a range of about 23-29 cm from said distal electrode.

8. The apparatus as described in claim 6, wherein said signal generatingmeans is further characterized in that said signals are negative at saidfirst terminal with respect to said second terminal, such that saiddistal electrode is the cathode and said proximal electrode is theanode, whereby cathodal pacing of the heart is achieved when saidcatheter is positioned such that said distal electrode is within thepatients heart and said proximal electrode is within the patient andoutside of the patients heart.

9. The apparatus as described in claim 6, wherein said signal generatingmeans is a demand type pacing generator.

10. A method of artificially pacing a human patient comprisingperiodically generating outside of said patient electrical pacingsignals, positioning a first electrode at a first position within saidpatients heart and a second electrode at a second position within saidpatient's vascular system but outside of said patients heart,transmitting said signals into said patient and connecting them to saidelectrodes with said signals being negative at said first position withrespect to said second position.

H. The method as described in claim 10 wherein said first electrode hasa first surface of a predetermined area, and said second electrode has asurface area greater than said first surface, and comprisingdistributing the electric field generated at said second electrode alongsaid second electrode.

12. The method as described in claim 10, comprising periodicallygenerating pacing signals with a demand pacer, and also sensingbiopotentials at said first and second positions and developingtherefrom biopoten- 40 tial signals, coupling said biopotential signalsto'said demand pacer, and generating with said demand pacer saidelectrical pacing signals as a function of said sensed biopotentialsignals.

[3. The method as described in claim 7 wherein said first position is inthe right ventricle of the patients heart.

14. The method as described in claim 10 wherein said positioning stepcomprises positioning a bipolar catheter having said first and secondelectrodes thereon in said patient such that said first electrode iswithin said patients heart and said second electrode is at least 4 cmoutside of said patients heart, said method further including couplingsaid electrical pacing signals to said electrodes, whereby said patientis cathodally paced.

15. The method as described in claim 10, wherein said positioning stepcomprises positioning a catheter having first and second electrodesthereon in said patient such that said first electrode is positionedwithin the patients right ventricle.

16. A method of artificially pacing a human patient through a catheter,said catheter having first and second electrodes, with said firstelectrode being near one end of said catheter, comprising:

a. positioning within said patient a portion of said catheter, saidpositioning step including positioning said first electrode within saidpatient's heart and said second electrode within said patient andoutside of said patient's heart; b. maintaining the opposite end of saidcatheter outside of said patient; 5 c. periodically generating outsideof said patient bipolar pacing signals;

d. connecting said pacing signals to said catheter and transmitting saidsignals through said catheter to said electrodes so that said signalsappear across said electrodes, whereby said patient is paced.

17. The method as described in claim 16, wherein said pacing signals areconnected so that said pacing signals have a negative polarity at saidfirst electrode with respect to said second electrode, whereby saidpatient is cathodally paced.

18. The method as described in claim 17, wherein said positioning stepcomprises positioning said second electrode at least 4 cm outside of thepatients heart.

19. The method as described in claim 17, wherein said positioning stepcomprises positioning said second electrode within about cm from thepatient's heart.

20. A method of artificially pacing a human patient comprisingpositioning a bipolar catheter having first and second electrodes insaid patient such that said first electrode is positioned within saidpatients heart and said second electrode is positioned at least 4 cmoutside of said patients heart, periodically generating outside of saidpatient electrical pacing signals, connecting said electrical pacingsignals between said first electrode and said second electrode with saidsignals being negative at said electrode within said patients heart withrespect to said second electrode outside of said patient's heart,whereby said patient is cathodally paced.

21. The method as described in claim 20, comprising positioning saidfirst electrode in the right ventricle of said patients heart.

22. Catheter apparatus adapted to be positioned in a patient for use incardiac pacing of the patient, with a predetermined end extending intothe patients heart, comprising:

a. an elongated flexible catheter tube having two conducting leadsextending through respective lengths thereof;

b. a distal electrode of predetermined surface size positioned near saidpredetermined end of said catheter tube, and connected electrically to afirst of said leads; and

c. a proximal electrode positioned on said catheter,

said proximal electrode being at its distal end a distance of at leastabout 23 cm from said distal electrode, and connected electrically tothe second of said leads.

23. The apparatus as described in claim 22, further comprising:

a. signal generating means, for generating electrical pacing signals,said signal generating means having first and second terminals acrosswhich said electrical signals appear;

b. connecting means for connecting, at the end of said catheter oppositesaid predetermined end, said first lead to said first terminal and saidsecond lead to said second terminal; and

c. said signal generating means producing signals which are negative atsaid second terminal with respect to said first terminal, so as toprovide apparatus for cathodal pacing.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 893461 Dated July 8 1975 ln n fl Thomas A. Preston It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 6, line 51, after "patient," change "said" to and.

Signed and Sealed this twenty-eight Day of October 1975 [SEAL] A rtest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner nfPalemsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3 I 893 1 461 Dated July 8 1975 Inventor(s, Thomas A. PrestonIt is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 6, line 51, after "patient," change "said" to -and-. Column 7,line 45, change "7" to lO-.

Signed and Sealcd this Arrest:

RUTH C. MASON C. MARSHALL D Arresting Officer ANN (vmmissinner nj'Paremsand Trademarks

1. Catheter apparatus adapted to be positioned in a patient for use incardiac pacing of the patient, with a predetermined end extending intothe patieNt''s heart, comprising: a. an elongated flexible catheter tubehaving two conducting leads extending through respective lengthsthereof; b. a distal electrode of predetermined surface size positionednear said predetermined end of said catheter tube, and connectedelectrically to a first of said leads; and c. proximal electrodepositioned on said catheter at a distance at least about 23 cm from saiddistal electrode, and connected electrically to the second of saidleads.
 2. The apparatus as described in claim 1, wherein said proximalelectrode has a surface area at least 10 times as great as said distalelectrode.
 3. The apparatus as described in claim 2, wherein saidproximal electrode is positioned a distance within a range of 23-29 cmproximal from said distal electrode.
 4. The apparatus as described inclaim 1, wherein said proximal electrode extends less than 6 centimetersalong said catheter tube.
 5. The apparatus as described in claim 1,wherein said proximal electrode is of greater surface area than saiddistal electrode.
 6. Pacing apparatus adapted for generating electricalpacing signals outside of a patient, communicating said signals insideof the patient, said delivering said signals between a position withinthe heart of the patient and a position external to said heart,comprising: a. a catheter adapted for insertion into a patient, having adistal electrode positioned near a first end thereof, a proximalelectrode on said catheter and positioned a distance at least 23 cm fromsaid distal electrode, a first lead connecting said distal electrodewith the opposite end of said catheter, and a second lead connecting theproximal electrode with said opposite catheter end; b. signal generatingmeans, for generating electrical pacing signals, said signal generatingmeans having first and second terminals across which said electricalsignals appear; c. connecting means for connecting, at said opposite endof said catheter, said first lead to the first terminal of said signalgenerating means and said second lead to the second terminal of saidsignal generating means.
 7. The apparatus as described in claim 6,wherein said proximal electrode is positioned at a distance within arange of about 23-29 cm from said distal electrode.
 8. The apparatus asdescribed in claim 6, wherein said signal generating means is furthercharacterized in that said signals are negative at said first terminalwith respect to said second terminal, such that said distal electrode isthe cathode and said proximal electrode is the anode, whereby cathodalpacing of the heart is achieved when said catheter is positioned suchthat said distal electrode is within the patient''s heart and saidproximal electrode is within the patient and outside of the patient''sheart.
 9. The apparatus as described in claim 6, wherein said signalgenerating means is a demand type pacing generator.
 10. A method ofartificially pacing a human patient comprising periodically generatingoutside of said patient electrical pacing signals, positioning a firstelectrode at a first position within said patient''s heart and a secondelectrode at a second position within said patient''s vascular systembut outside of said patient''s heart, transmitting said signals intosaid patient and connecting them to said electrodes with said signalsbeing negative at said first position with respect to said secondposition.
 11. The method as described in claim 10 wherein said firstelectrode has a first surface of a predetermined area, and said secondelectrode has a surface area greater than said first surface, andcomprising distributing the electric field generated at said secondelectrode along said second electrode.
 12. The method as described inclaim 10, comprising periodically generating pacing signals with ademand pacer, and also sensing biopotentials at said first and secondpositions and developing therefrom Biopotential signals, coupling saidbiopotential signals to said demand pacer, and generating with saiddemand pacer said electrical pacing signals as a function of said sensedbiopotential signals.
 13. The method as described in claim 7 whereinsaid first position is in the right ventricle of the patient''s heart.14. The method as described in claim 10 wherein said positioning stepcomprises positioning a bipolar catheter having said first and secondelectrodes thereon in said patient such that said first electrode iswithin said patient''s heart and said second electrode is at least 4 cmoutside of said patient''s heart, said method further including couplingsaid electrical pacing signals to said electrodes, whereby said patientis cathodally paced.
 15. The method as described in claim 10, whereinsaid positioning step comprises positioning a catheter having first andsecond electrodes thereon in said patient such that said first electrodeis positioned within the patient''s right ventricle.
 16. A method ofartificially pacing a human patient through a catheter, said catheterhaving first and second electrodes, with said first electrode being nearone end of said catheter, comprising: a. positioning within said patienta portion of said catheter, said positioning step including positioningsaid first electrode within said patient''s heart and said secondelectrode within said patient and outside of said patient''s heart; b.maintaining the opposite end of said catheter outside of said patient;c. periodically generating outside of said patient bipolar pacingsignals; d. connecting said pacing signals to said catheter andtransmitting said signals through said catheter to said electrodes sothat said signals appear across said electrodes, whereby said patient ispaced.
 17. The method as described in claim 16, wherein said pacingsignals are connected so that said pacing signals have a negativepolarity at said first electrode with respect to said second electrode,whereby said patient is cathodally paced.
 18. The method as described inclaim 17, wherein said positioning step comprises positioning saidsecond electrode at least 4 cm outside of the patient''s heart.
 19. Themethod as described in claim 17, wherein said positioning step comprisespositioning said second electrode within about 10 cm from the patient''sheart.
 20. A method of artificially pacing a human patient comprisingpositioning a bipolar catheter having first and second electrodes insaid patient such that said first electrode is positioned within saidpatient''s heart and said second electrode is positioned at least 4 cmoutside of said patient''s heart, periodically generating outside ofsaid patient electrical pacing signals, connecting said electricalpacing signals between said first electrode and said second electrodewith said signals being negative at said electrode within saidpatient''s heart with respect to said second electrode outside of saidpatient''s heart, whereby said patient is cathodally paced.
 21. Themethod as described in claim 20, comprising positioning said firstelectrode in the right ventricle of said patient''s heart.
 22. Catheterapparatus adapted to be positioned in a patient for use in cardiacpacing of the patient, with a predetermined end extending into thepatient''s heart, comprising: a. an elongated flexible catheter tubehaving two conducting leads extending through respective lengthsthereof; b. a distal electrode of predetermined surface size positionednear said predetermined end of said catheter tube, and connectedelectrically to a first of said leads; and c. a proximal electrodepositioned on said catheter, said proximal electrode being at its distalend a distance of at least about 23 cm from said distal electrode, andconnected electrically to the second of said leads.
 23. The apparatus asdescribed in claim 22, further comprising: a. siGnal generating means,for generating electrical pacing signals, said signal generating meanshaving first and second terminals across which said electrical signalsappear; b. connecting means for connecting, at the end of said catheteropposite said predetermined end, said first lead to said first terminaland said second lead to said second terminal; and c. said signalgenerating means producing signals which are negative at said secondterminal with respect to said first terminal, so as to provide apparatusfor cathodal pacing.